This invention relates to a heat resistant resin composition and a film or a sheet thereof and a laminate comprising the film or the sheet as a substrate.
A crystalline polyarylketone resin, typically polyetheretherketone, is excellent in heat resistance, flame retardant property, hydrolysis resistance, and chemical resistance, and, therefore, widely used mainly for aircraft parts, electric parts or electronic parts. However, raw materials for the polyarylketone resin are very expensive. Further, a glass transition temperature of the resin is so low as about 140xc2x0 C. to 170xc2x0 C. For this reason, various attempts have been, made to further improve heat resistance of the resin, among which a blend of the resin with a noncrystalline polyetherimide resin has attracted attentions. For instance, Japanese Patent Application Laid-open No. 59-187054/1984 and National Publication of PCT Application No. 61-500023/1986 disclose compositions of the crystalline polyarylketone resin with the noncrystalline polyetherimide resin; Japanese Patent Application Laid-open No. 59-115353/1984 describes that those compositions are useful for a substrate of a circuit board; Japanese Patent Application Laid-open No. 2000-38464 and Japanese Patent Application Laid-open No. 2000-200950 by the present inventors disclose a printed wiring board comprising the aforesaid composition and a production method thereof.
A flexible printed wiring board made of a film or sheet of the composition of the crystalline polyarylketone resin and the noncrystalline polyetherimide resin, which composition usually comprises an inorganic filler to improve dimensional stability, is good in dimensional stability and heat resistance. However, its mechanical strength, especially edge tearing resistance, is not satisfactory, which results in poor folding resistance or bending resistance. Therefore, reliable electrical connection is not secured, and the board has only limited applications. This problem needs to be solved. The aforesaid patent publications neither describe nor suggest causes or solutions of the problem.
Thus, an object of the present invention is to provide a heat resistant resin composition, a film or sheet thereof and a laminate comprising the film or sheet as a substrate, which are suitable for an electronic part such as a flexible printed wiring board.
The present inventors have found that the above problem can be solved by a resin composition which has a specific dynamic viscoelasticity and comprises a crystalline polyarylketone resin and a noncrystalline polyetherimide resin.
Thus, the present invention is a heat resistant resin composition comprising 70 to 30 wt % of a crystalline polyarylketone resin having a peak crystalline melting temperature of 260xc2x0 C. or higher and 30 to 70 wt % of a noncrystalline polyetherimide resin, wherein said composition has at least 2 peaks of loss tangent (tanxcex4) between 140xc2x0 C. and 250xc2x0 C., determined by dynamic mechanical measurement. In a preferred embodiment, the crystalline polyarylketone resin is a polyetheretherketone resin having structural repeating units of the formula (1) and the noncrystalline polyethermide resin is a polyetherimide resin having structural repeating units of the formula (2). 
Further, the present invention is a heat resistant film or sheet composed of the aforesaid heat resistant resin composition.
Still further, the present invention is a laminate comprising at least one aforesaid heat resistant film or sheet and at least one conductive film bonded on at least one side of the heat resistant film or sheet by heat bonding without an intermediary adhesive layer. Preferably, the heat resistant film or sheet as a substrate of the laminate has a edge tearing resistance of 60N or larger both in a longitudinal direction and a transversal direction, determined according to the edge tearing resistance test specified in the Japanese Industrial Standard C2151.